(Received 28 October 2010;accepted 29 November 2010;online 4 December 2010)

In the title compound, C20H13NO, the indene ring is disordered over two sites with an occupancy ratio of 0.557 (2):0.443 (2). Both disordered components of indene are nearly perpendicular to the naphthalene ring system, making dihedral angles of 90.9 (2) and 85.0 (5)°. The five-membered ring of the 1H-pyrrol-2(3H)-one adopts an envelope conformation with the spiro C atom at the flap position. Inter­molecular classical N—H⋯O and weak C—H⋯O hydrogen bonding is present in the crystal structure.

In the past decades, spiro lactams have been attracted considerable interest because they are commonly found as subunits of many natural products. Some of them have significant biological activities, including multiple drug resistance reversing, antifungal and antitumor activities (Tsuda et al.,2004). Synthetic methods directed to these classes of spiro lactam compounds have been developed (Ready et al., 2004). Among them, spiro cyclizations of N-acyliminium ions with an internalalkene nucleophile were first described by Speckamp (Schoemaker et al., 1978). Reductive coupling of acrylates with isocyanates to furnish spiro lactam skeleton was used by Wood [Ready et al., 2004]. The title compound I was synthesized in one step through a new ring-rearrangement reaction. It was undertaken as a continuation of our efforts towards synthesis of dibenzoxanthenes which exhibit a wide variety of biological activities [Chen et al., 2005].

The asymmetric unit of I contains one independent spiro-[indene-1,3'-(2',3'-dihydro-2'-oxa-benzo[e]indole)] molecule. In the complex I, the naphthyl ring and indene ring are almost perpendicular to each other, making a diheral angle of 90.9 (2)°. All bond lengths and bond angles are in the normal ranges and comparable to those observed in the similar substituted spiro-[indene-1,3'-(2',3'-dihydro-2'-oxa-benzo[e]indole)], except the disordered part of indene ring. The C(11)=O(1) bond length of 1.215 (4) Å of oxa-indole moiety conforms to the value for a double bond.

In the crystal of I, there are two types hydrogen bonding interactions: one type is classical hydrogen bonding between O(1) atom and N(1) atom from oxa-benzo[e]indole moiety, the other one is unclassical hydrogen bonding between O(1) atom and C(18) atom from the phenyl group. The molecule I was linked together by a double strong classical intermolecular hydrogen bonds of N(1)—H1A···O(1), thereby forming a dimer structure, while the dimers were futher linked by the unclassical hydrogen bonds of C(18)—HA···O(1), thereby forming a two dimessional network structure.

Into a stirred solution of CuCl2.2H2O (17 mg, 0.1 mmol) in methanol (5 ml) was added a solution of ethanolamine (6 mg, 0.1 mmol) in methanol (2 ml). After 10 min. a solution of 2-amino-2'-hydroxy-1,1'-binaphthyl (0.1 mmol) in methanol (2 ml) was added and the reaction mixture was stirred at 323 K. When the reaction was completed, the solvent was removed under reduced pressure. The residue was extracted with AcOEt (10 ml), washed with 5% ammonia (10 ml) and water (10 ml), then dried with Na2SO4, and the solvent was removed under reduced pressure. Thick layer chromatography of the residue (hexane:ethyl acetate, 10:1) followed by recrystallization from acetone gave the title complex as red crystals. Yield: ca 82%.

The indene ring was found to be disordered over two sites, occupancies were refined to 0.557 (2):0.443 (2). The distance restraints have been used to make these two disordered indene ring with same bond lengths and same displacement parameters. H atoms were positioned geometrically with N—H = 0.86 and C—H = 0.93 Å, and refined using riding-model approximation with Uiso(H) = 1.2Ueq(C,N).

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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